What is 21.5 percent of 645 - step by step solution

To get the solution, we are looking for, we need to point out what we know.

1. We assume, that the number 645 is 100% - because it's the output value of the task.
2. We assume, that x is the value we are looking for.
3. If 645 is 100%, so we can write it down as 645=100%.
4. We know, that x is 21.5% of the output value, so we can write it down as x=21.5%.
5. Now we have two simple equations:
1) 645=100%
2) x=21.5%
where left sides of both of them have the same units, and both right sides have the same units, so we can do something like that:
645/x=100%/21.5%
6. Now we just have to solve the simple equation, and we will get the solution we are looking for.

7. Solution for what is 21.5% of 645

645/x=100/21.5
(645/x)*x=(100/21.5)*x       - we multiply both sides of the equation by x
645=4.6511627906977*x       - we divide both sides of the equation by (4.6511627906977) to get x
645/4.6511627906977=x
138.675=x
x=138.675

now we have:
21.5% of 645=138.675